Sealing method for high-flow water inrush at side wall of foundation pit

Abstract

The present invention relates to a sealing method for high-flow water inrush at a side wall of a foundation pit, the method comprising: calculating the minimum radius of a counter-pressure soil berm on the basis of the flow time of a liquid slurry in the counter-pressure soil berm being not less than the chemical setting time of the liquid slurry; piling up filtering sand bags on a foundation pit excavation face at a water inrush point, and constructing the counter-pressure soil berm; constructing annular grouting holes at the foundation pit on the outside of support piles and a cut-off curtain; according to the planar arrangement of the annular grouting holes, successively injecting a double-liquid slurry formed by mixing a cement slurry and sodium silicate into the annular grouting holes; inspecting the water seepage condition on the periphery of the counter-pressure soil berm until no water seepage occurs on the periphery of the counter-pressure soil berm; and excavating the counter-pressure soil berm layer by layer until the excavation reaches the pit bottom without water seepage observed at a side wall of the foundation pit. The present invention has the beneficial effects that: the size of the counter-pressure soil berm is optimally designed on the basis of the condition that the flow time of the double-liquid slurry in the soil berm is longer than the setting time, so as to solve the problems of slurry setting failure and poor grouting and sealing effects, thus saving a large amount of grouting materials, and reducing economic loss caused by secondary sealing.

Description

A method for sealing large-flow water inrush on the sidewall of a foundation pit Technical Field

[0001] This invention relates to the fields of construction, transportation and water conservancy engineering technology, and specifically to a method for sealing large-flow water inrush on the sidewall of a foundation pit. Background Technology

[0002] Support piles combined with cement mixing piles are a common support method and water-stopping measure for deep foundation pits. However, due to uneven soil sedimentation and uneven cement mixing piles, water leakage from the water-stop curtain is a common quality defect. This is especially true when the foundation pit is deep and contains a confined aquifer, making it prone to large-volume water inrushes along the sidewalls, accompanied by sediment loss, damaging the surrounding environment and even causing the foundation pit support structure to collapse. In the event of a large-volume water inrush, the large volume of water, along with the sediment, quickly floods the foundation pit, causing equipment to be submerged and threatening the lives of workers. Improper or untimely handling can result in economic losses that the construction company cannot afford.

[0003] In response to large-volume water inrushes in foundation pits, due to the large volume and sudden occurrence of the inrushes, often accompanied by sediment loss, the situation is urgent. To prevent the situation from worsening, a physical sealing method of backfilling and counter-pressure with soil is typically used to ensure the stability of the foundation pit support structure, followed by chemical sealing with cement grout and water glass. However, the height and dimensions of the backfill counter-pressure are primarily designed to ensure the stability of the foundation pit support structure and prevent further displacement. This can lead to the cement and water glass grout failing to solidify and seeping from the counter-pressure platform slope, resulting in insufficient grouting pressure, significant waste of grouting materials, and a continued risk of water inrushes during subsequent excavation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for sealing large-flow water inrush on the sidewall of a foundation pit. Based on the condition that the flow time of the two-liquid grout in the soil platform is greater than the solidification time, the size of the counter-pressure soil platform is optimized, thereby solving the problems of grout not being able to solidify and poor grouting sealing effect, saving a lot of grouting materials and reducing the economic losses caused by secondary sealing.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for sealing large-flow water inrush on the sidewall of a foundation pit includes the following steps:

[0007] S1. Locate and determine the position of the water inrush point on the side wall of the foundation pit;

[0008] S2. Calculate the minimum radius of the counterweight platform based on the fact that the flow time of the slurry in the counterweight platform is not less than the chemical solidification time of the slurry. Stack filter sandbags on the excavation face of the foundation pit at the water inflow point, and then fill the counterweight platform around the filter sandbags, while keeping the water level difference between the inside and outside of the foundation pit no more than 2.0m.

[0009] S3. Construct annular grouting holes at the foundation pit outside the support piles and water-stop curtain, and lower double-pipe grouting pipes into the annular grouting holes.

[0010] S4. Cement grout and water glass are injected into the bottom of a single grouting hole through a double-pipe grouting pipe and mixed to form a two-liquid grout. The grouting pressure is used to make the two-liquid grout seep into the water inflow channel until the two-liquid grout solidifies and the grout can no longer be injected, thus completing the grouting and sealing of a single grouting hole.

[0011] S5. Following the planar arrangement of the annular grouting holes, repeat steps S4 to S5 to drill and grout the next grouting hole until each grouting hole is grouted and sealed.

[0012] S6. Drain the water in the foundation pit and check the seepage around the counterweight soil platform. If the seepage is large, make new grouting holes between the grouting holes that have been grouted and repeat steps S4 to S6 until there is no seepage around the counterweight soil platform.

[0013] S7. Excavate the counterweight platform in layers, with each layer having an excavation depth of no more than 2.0m. If no water seepage is observed on the sidewalls of the pit when the excavation reaches the bottom, the water seepage point has been successfully sealed.

[0014] Furthermore, the calculation of the minimum radius of the counterweight earth platform includes the following steps:

[0015] S21. Measure the flow velocity V0 of the water at the water inrush point before the filter sandbags are piled up;

[0016] S22. Based on the properties of the soil resistance to water flow in the counterweight earth platform, the soil resistance coefficient is introduced, and the average flow velocity V of the water flow in the counterweight earth platform is calculated according to the formula V=V0 / β, where β is the soil resistance coefficient.

[0017] S23. Calculate the shortest time t required for water to flow from the water inflow point at the support pile to the outlet of the counterweight soil platform slope according to the formula t=S / V, where S is the shortest distance from the water inflow point at the support pile to the outlet of the counterweight soil platform slope.

[0018] S24. Introduce a safety factor based on the chemical sealing conditions of the water inrush point, and calculate the flow time t of the two-component slurry in the counter-pressure earth platform according to the formula t=αt0, where t0 is the chemical solidification time of the two-component slurry, α is the safety factor and α≥1;

[0019] S25, According to formula R min =S=αVt0=αV0t0 / β Calculate the minimum radius R of the counterweight earth platform min .

[0020] Furthermore, the radius of the filter sandbags at the water inflow point is 1.0m to 2.0m, and the stacking height is not less than 2.0m.

[0021] Furthermore, when constructing the counterweight platform, the water inrush point is taken as the center, and the minimum radius of the counterweight platform is taken as the upper arc radius of the counterweight platform. The slope ratio of the counterweight platform is not greater than 1:1, and the height of the counterweight platform is not less than the water head height in the foundation pit and not less than the minimum radius of the counterweight platform.

[0022] Furthermore, the slope of the counterweight platform is protected by piling up counterweight sandbags.

[0023] Furthermore, the annular grouting holes are arranged on the outside of the foundation pit, 1.0m to 3.0m away from the water-stop curtain, and the drilling depth extends at least 1.0m below the water inflow point.

[0024] Furthermore, when arranging the annular grouting holes, the water inrush point at the water-stop curtain is taken as the center, and the annular grouting holes are arranged on the semicircle with a radius of 1.0m to 3.0m, and the hole spacing is 0.5m to 1.0m.

[0025] Furthermore, the drilling spacing of the annular grouting holes is determined according to the amount of water inflow. When the water inflow is large, the drilling spacing is small and the number of holes is not less than 3.

[0026] Furthermore, the dual-pipe grouting system includes a water glass grouting pipe and a cement grouting pipe.

[0027] Furthermore, the grouting concentration of the cement grout and water glass two-component grout is initially thick and then thinned.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Based on the condition that the flow time of the liquid slurry in the counterweight platform is greater than the chemical solidification time of the liquid slurry, the present invention optimizes the size design of the counterweight platform, which solves the problem of waste of grouting material caused by the failure of the dual liquid slurry to solidify when it flows out of the slope of the counterweight platform.

[0030] 2. This invention combines physical and chemical sealing. When a large flow of water is detected, it can quickly respond to emergencies by piling up filter sandbags at the water inrush point to prevent the loss of silt from the back of the foundation pit and its impact on the surrounding environment. Then, a counterweight earth platform is built to ensure the stability of the support structure. The counterweight earth platform is used to extend the slurry flow channel and ensure the successful sealing of the water inrush channel on the side wall of the foundation pit.

[0031] 3. This invention improves the grouting sealing effect and safety by introducing a safety factor for the counter-pressure soil platform, with a safety factor value of 1.1 to 1.3. Attached Figure Description

[0032] Figure 1 is a plan view of the high-flow-rate water inrush point on the side wall of the foundation pit in this invention;

[0033] Figure 2 is a cross-sectional schematic diagram of the high-flow-rate water inrush point on the side wall of the foundation pit in this invention;

[0034] Figure 3 is a schematic diagram of the planar structure of the filter layer at the water inflow point in this invention;

[0035] Figure 4 is a schematic cross-sectional view of the filter layer at the water inflow point in this invention.

[0036] Figure 5 is a schematic diagram of the planar structure of the counter-pressure earth platform in this invention;

[0037] Figure 6 is a schematic cross-sectional view of the counter-pressure earth platform in this invention;

[0038] Figure 7 is a schematic diagram of the planar layout of the annular grouting holes outside the water-stopping curtain in this invention;

[0039] Figure 8 is a schematic cross-sectional view of the annular grouting holes outside the water-stop curtain in this invention.

[0040] Figure 9 is a schematic diagram of the state during grouting and sealing in this invention.

[0041] In the diagram: 101, support pile; 102, water-stop curtain; 103, excavation face of foundation pit; 104, sand layer; 2, water inrush point; 301, filter sandbag; 302, counterweight platform; 303, counterweight sandbag; 4, annular grouting hole; 501, water glass grouting pipe; 502, cement grouting pipe; 6, grouting vein. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0043] As shown in Figures 1 to 9, a method for sealing large-flow water inrushes on the sidewall of a foundation pit involves first physically sealing the water inrush point 2 by piling up filter sandbags 301, filling a counterweight platform 302, and counterweight sandbags 303 at the water inrush point 2; then, injecting a two-component grout mixture of cement grout and water glass into the grouting boreholes around the support piles 101 and the water-stop curtain 102, and chemically sealing the water inrush point 2 with large flow and high head pressure by forming grouting veins 6 through the chemical solidification of the two-component grout in the water inrush channel.

[0044] The specific sealing process includes the following steps:

[0045] S1. As shown in Figures 1 and 2, locate and determine the position of water inrush point 2 on the side wall of the foundation pit;

[0046] S2. As shown in Figures 3 to 6, the minimum radius of the counterweight platform 302 is calculated based on the principle that the flow time of the slurry within the counterweight platform 302 should not be less than the chemical solidification time of the slurry. Filter sandbags 301 are piled up on the excavation face 103 of the foundation pit at water inflow point 2, and then the counterweight platform 302 is constructed around the filter sandbags 301 to reduce the water inflow rate. Simultaneously, water is pumped out of the foundation pit to maintain the water level difference h3 between the inside and outside of the pit at no more than 2.0m. The specifications and model of the water pump can be selected based on the water flow rate Q at water inflow point 2.

[0047] Specifically, the stacking radius of the filter sandbags 301 at water inflow point 2 is 1.0m to 2.0m, and the stacking height is not less than 2.0m. When filling the counterweight platform 302, the water inflow point 2 is the center, and the minimum radius of the counterweight platform 302 is the upper arc radius of the counterweight platform 302. The slope ratio of the counterweight platform 302 is not greater than 1:1, and the height H of the counterweight platform 302 is not less than the water head height h1 in the foundation pit and not less than the minimum radius of the counterweight platform 302. At the same time, the slope of the counterweight platform 302 is protected by stacking counterweight sandbags 303.

[0048] By stacking sandbags 301, a filter layer is formed at the water inflow point 2. The filter layer prevents the loss of mud and sand in the sand layer 104 on the back of the support piles 101 and the water-stop curtain 102, thus preventing the collapse of the soil outside the foundation pit and the structural damage of the support piles 101.

[0049] S3. As shown in Figures 7 and 8, annular grouting holes 4 are constructed at the foundation pit outside the support piles 101 and the water-stop curtain 102, and double-pipe grouting pipes are lowered into the annular grouting holes 4.

[0050] Specifically, the annular grouting holes 4 are arranged outside the support piles 101 and the water-stop curtain 102, at a distance of 1.0m to 3.0m from the water-stop curtain 102, and the drilling depth is not less than 1.0m below the water inflow point 2. When arranging the annular grouting holes 4, the water inflow point 2 at the water-stop curtain 102 is taken as the center, and the annular grouting holes 4 are arranged on a semicircle with a radius of 1.0m to 3.0m. The drilling spacing of the annular grouting holes 4 is kept within the range of 0.5m to 1.0m. The specific drilling spacing can be determined according to the size of the water inflow. When the water inflow is large, the drilling spacing should be small and the number of holes should not be less than 3.

[0051] S4. As shown in Figure 9, cement grout and water glass are injected into the bottom of a single grouting hole through a double-pipe grouting pipe and mixed to form a double-liquid grout. The double-liquid grout is then allowed to seep into the water inflow channel by the grouting pressure until the double-liquid grout solidifies and can no longer be injected, thus completing the grouting of a single annular grouting hole 4.

[0052] Specifically, the dual-pipe grouting system includes a water glass grouting pipe 501 and a cement grouting pipe 502. After both pipes are simultaneously lowered into a single grouting pipe, a grouting pump injects cement grout and water glass into the grouting hole through the cement grouting pipe 502 and the water glass grouting pipe 501, respectively. The cement grout and water glass mix at the bottom outlet to form a dual-liquid grout. Under grouting pressure, the dual-liquid grout seeps into the water inflow channel. As the dual-liquid grout solidifies to form grouting veins 6, the grouting pressure gradually increases. Grouting is stopped when the pressure becomes too high to continue. During the grouting process, the concentration of the cement grout and water glass dual-liquid grout is initially thick and then thins. The counterweight platform 302 not only ensures the stability of the support structure but also extends the flow channel of the grout, thereby ensuring successful sealing of the water inflow channel.

[0053] S5. Following the planar arrangement of the annular grouting holes 4, repeat steps S4 to S5 to drill and grout the next annular grouting hole 4 until each annular grouting hole 4 is grouted and sealed.

[0054] S6. Drain the water in the foundation pit and check the seepage around the counterweight soil platform 302. If the seepage is large, make additional grouting holes between the already grouted annular grouting holes 4, and repeat steps S4 to S6 until there is no seepage around the counterweight soil platform 302.

[0055] S7. Excavate the counterweight soil platform 302 in layers, with each layer having an excavation depth of no more than 2.0m. If water seepage is still not observed on the side wall of the foundation pit when the excavation reaches the bottom, then the water seepage point 2 has been successfully sealed.

[0056] To address the problem of wasted grouting material caused by the failure of the dual-liquid grout to solidify after flowing out from the slope of the counterweight platform, this invention optimizes the dimensions of the counterweight platform 302 based on the principle that the flow time of the grout within the platform 302 should not be less than its chemical solidification time. The main design calculation focuses on the minimum radius of the counterweight platform 302. The specific design and calculation process includes the following steps:

[0057] S21. Measure the flow velocity V0 and flow rate Q of the water at two water inflow points before the reverse filter sandbags 301 are piled up;

[0058] S22. Based on the properties of the soil resistance to water flow in the counterweight earth platform 302, a soil resistance coefficient is introduced, and the average flow velocity V of the water in the counterweight earth platform 302 is calculated according to the formula V=V0 / β, where β is the soil resistance coefficient, which can be selected according to the known soil type or measured by existing measurement methods.

[0059] S23. Calculate the shortest time t required for water to flow from the water inflow point 2 at the support pile 101 to the outlet of the slope of the counterweight earth platform 302 according to the formula t=S / V, where S is the shortest distance from the water inflow point 2 at the support pile 101 to the outlet of the slope of the counterweight earth platform 302.

[0060] S24. Based on the chemical sealing conditions of water inrush point 2, a safety factor is introduced, and the flow time t of the two-component grout within the counterweight platform 302 is calculated according to the formula t = αt0, where t0 is the chemical solidification time of the two-component grout, and α is the safety factor, α ≥ 1. In practical applications, the preferred value of α is 1.1 to 1.3.

[0061] S25, According to formula R min =S=αVt0=αV0t0 / β Calculate the minimum radius R of the counterweight earthwork platform 302. min .

[0062] Based on the above-mentioned method for sealing large-flow water inrush on the sidewall of the foundation pit, this invention, after discovering water inrush point 2, combines physical and chemical sealing methods to seal water inrush point 2. This can prevent the loss of mud and sand on the outside of the support pile 101 and reduce the water inrush flow, effectively preventing the foundation pit water inrush danger from worsening. At the same time, by optimizing the size design of the counterpressure platform 302, the grouting sealing effect and safety are improved, and the problem of waste of grouting material caused by the inability of the dual-liquid grout to solidify when flowing out from the slope of the counterpressure platform is also solved.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for sealing large-flow water inrush on the sidewall of a foundation pit, characterized in that, Includes the following steps: S1. Locate and determine the location of the water inrush point (2) on the side wall of the foundation pit; S2. Calculate the minimum radius of the counterweight platform (302) based on the fact that the flow time of the slurry in the counterweight platform (302) is not less than the chemical solidification time of the slurry. Stack the filter sandbags (301) on the excavation face (103) of the foundation pit at the water inrush point (2), and then fill the counterweight platform (302) around the filter sandbags (301) while keeping the water level difference between the inside and outside of the foundation pit no greater than 2.0m. S3. Construct annular grouting holes (4) at the foundation pit outside the support piles (101) and the water-stop curtain (102), and lower double-pipe grouting pipes into the annular grouting holes (4). S4. Cement grout and water glass are injected into the bottom of a single grouting hole through a double-pipe grouting pipe and mixed to form a two-liquid grout. The grouting pressure is used to make the two-liquid grout seep into the water inflow channel until the two-liquid grout solidifies and the grout can no longer be injected, thus completing the grouting and sealing of a single grouting hole. S5. According to the planar arrangement of the annular grouting holes (4), repeat steps S4 to S5 to drill and grout the next grouting hole until each grouting hole is grouted and sealed. S6. Drain the water in the foundation pit and check the seepage around the counterweight soil platform (302). If the seepage is large, make new grouting holes between the grouting holes that have been grouted and repeat steps S4 to S6 until there is no seepage around the counterweight soil platform (302). S7. Excavate the counter-pressure platform (302) in layers. The excavation depth of each layer shall not exceed 2.0m. When the excavation reaches the bottom of the pit, if there is still no water seepage on the side wall of the pit, the water inrush point (2) is successfully sealed.

2. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, The minimum radius of the counterweight earthwork platform (302) is calculated by the following steps: S21. Measure the flow velocity V0 of the water at the water inrush point (2) before the reverse filter sandbags (301) are piled up; S22. Based on the properties of the soil resistance to water flow in the counterweight earth platform (302), the soil resistance coefficient is introduced, and the average flow velocity V of the water flow in the counterweight earth platform (302) is calculated according to the formula V=V0 / β, where β is the soil resistance coefficient. S23. Calculate the shortest time t required for water to flow from the water inrush point (2) at the support pile (101) to the outlet of the slope of the counterweight earth platform (302) according to the formula t=S / V. In the formula, S is the shortest distance from the water inrush point (2) at the support pile (101) to the outlet of the slope of the counterweight earth platform (302). S24. Based on the chemical sealing conditions of the water inrush point (2), a safety factor is introduced, and the flow time t of the two-liquid slurry in the counter-pressure earth platform (302) is calculated according to the formula t=αt0, where t0 is the chemical solidification time of the two-liquid slurry, α is the safety factor and α≥1; S25, According to formula R min =S=αVt0=αV0t0 / β Calculate the minimum radius R of the counterweight earthwork platform (302) min .

3. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, The stacking radius of the filter sandbags (301) at the water inflow point (2) is 1.0m to 2.0m, and the stacking height is not less than 2.0m.

4. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, When filling the counterweight platform (302), the filling is carried out with the water inrush point (2) as the center and the minimum radius of the counterweight platform (302) as the upper arc radius of the counterweight platform (302). The slope ratio of the counterweight platform (302) is not greater than 1:1, and the height of the counterweight platform (302) is not less than the water head height in the foundation pit and not less than the minimum radius of the counterweight platform (302).

5. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that: The slope of the counterweight platform (302) is protected by piling up counterweight sandbags (303).

6. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, The annular grouting hole (4) is arranged on the outside of the foundation pit, 1.0m to 3.0m away from the water-stop curtain (102), and the drilling depth is not less than 1.0m below the water inrush point (2).

7. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 6, characterized in that, When arranging the annular grouting holes (4), take the water inrush point (2) at the water-stop curtain (102) as the center and the radius as 1.0m to 3.0m, and arrange the annular grouting holes (4) on the semicircle. The drilling spacing is 0.5m to 1.0m.

8. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 7, characterized in that, The drilling spacing of the annular grouting holes (4) is determined according to the amount of water inflow. When the amount of water inflow is large, the drilling spacing should be small and the number of holes should not be less than 3.

9. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, The dual-pipe grouting system includes a water glass grouting pipe (501) and a cement grouting pipe (502).

10. The method for sealing large-flow water inrush on the sidewall of a foundation pit according to claim 1, characterized in that, The grouting concentration of the cement grout and water glass two-component grout should be thickened first and then thinned.

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